The present invention relates to a steering column support assembly for supporting a steering column of a motor vehicle.
Motor vehicle dashboard assemblies, including the steering wheel and associated support structure, are normally assembled prior to insertion as a unit into the motor vehicle on an assembly line. The support assembly includes a support member that extends laterally with mounting points at left and right ends of the member for connection to fixing points on the motor vehicle chassis forward of the left and right front doors, at the so-called xe2x80x9cA-pillarsxe2x80x9d.
Although the support assembly may be used to support part of the dashboard, and components within the dashboard such as a heater unit, the main structural function of the support assembly is to support the steering wheel column, which extends downwards and away from the steering wheel through intervening structures, for example through a firewall between an engine compartment and a passenger compartment. Usually, such intervening structures do not provide direct support to the steering wheel column.
The largest external forces that can be expected to impinge on a steering wheel and steering wheel column are those resulting from a motor vehicle accident. These forces may tend to make the steering column and steering wheel rotate more towards the vertical, which can reduce driver safety. The steering wheel will normally be provided with a driver airbag, and so the steering column and support assembly must be able to bear the forces of the driver against the airbag during a collision.
As a result of these various requirements, steering column support assemblies have been developed that consist of a single tubular steel support member that extends laterally between the A-pillars. The tubular member has a bracket on a lower side of the member to which the steering column is fixed, and a fixing point above the steering column bracket that is used to affix the support assembly to chassis, for example to an upper portion of a firewall between the passenger compartment and the engine compartment. The tubular steel member may be straight or have a series of small bends and is hollow with a circular cross section. The bracket for the steering column, and any other fixing points along the length of the support structure, for example for a car stereo unit or heater/air conditioning unit, must be welded to the tubular steel member.
Welding such an assembly by hand is a skilled job. The welds must be accurately formed, and not adversely affect the structural integrity of the tubular member. When the manufacturer is designing the initial prototype of such a conventional steering column support structure, the time taken to make by hand a finished steering column support structure is a significant constraint.
Hand welding is of course not economic in large-scale production, and so robot welding is used in such circumstances. However a welding machine specially adapted to produce such a steering column support assembly is expensive to buy and to set up for a particular welding job. It may also not be easy to modify or adapt an existing design, for example to accommodate changes in the design of a dashboard or consumer units housed within the dashboard such as a heater, air conditioner, or in-car entertainment system.
It is an object of the invention to provide a steering column support assembly that addresses these issues.
According to the invention, there is provided a steering column support assembly for supporting a steering column of a motor vehicle, comprising a laterally extending support structure, mounting points for affixing opposite ends of the support structure to side portions of a motor vehicle chassis, a fixing point above the laterally extending support structure for affixing the support structure to a front portion of a motor vehicle chassis, and a steering column support bracket, the steering column support bracket being supported by the laterally extending support structure, wherein: the support structure includes a laterally extending first support member, and a laterally extending second support member; the first support member and the second support member each extend laterally between the mounting points; and the steering column support bracket braces apart the first support member and the second support member.
The use of two laterally extending support members is advantageous in several ways. First, it is not necessary that such a structure be welded together. The first and second support members can, for example, be bolted to the steering column support bracket. Second, the use of two spaced apart support members makes it easier to support other components within or beneath the dashboard. Finally, this structure permits a weight reduction compared with a single laterally extending support structure of similar strength and stiffness.
In a preferred embodiment of the invention, the steering column support bracket is supported by the first support member and the second support member respectively at a first location in the support assembly and at a second location in the support assembly, with the fixing point being at a third location in the support assembly. The first, second and third locations are arranged in a triangle formation when viewed along the lateral extent of the support members. This provides stiffness to help minimise forward rotation of the steering column in the event of a collision.
The laterally extending support structure may also provide support for one or more other mounting brackets for supporting consumer units within a dashboard. The mounting brackets may extend between the first support member and the second support member, or extend just from one of the support members. For example, a heater unit or in-car entertainment system, may be supported by one or more mounting brackets that extend transversely between the first and second mounting members. Accelerator, brake or clutch pedals may be supported by a bracket that extends downwardly from a lower one of the support members.
In order to facilitate connection of the steering column support bracket, and any other support brackets, to the laterally extending support structure, the first support member and the second support member may both be straight metallic or plastic hollow tubular members with a square cross-section, a rectangular cross-section, or a U-shaped cross-section.
Also according to the invention, there is provided a motor vehicle dashboard assembly, comprising a fascia, a steering column, and a steering column support assembly, wherein the steering column support assembly supports the steering column, and the steering column support assembly is according to the invention described above.
The steering column support assembly preferably also supports also at least in part the xe2x80x9cfasciaxe2x80x9d, i.e., the front panel or panels of the dashboard.